This invention relates to a control mechanism having spring means and an instantaneously heat-responsive bimetal member used in a drive fluid coupling for cooler fan blades of an engine of vehicles, such as automobiles or the like.
Japanese patent publication No. 47214/74 (filed as application No. 74442/67) discloses a drive fluid coupling for cooler fan blades of an engine of vehicles, such as automobiles or the like having an attachment base disposed on the front face of a casing closure is provided with a cup-shaped, snap spring-like heat-responsive bimetal member of an apex centering, deformable concavo-convex section attached in engagement of its peripheral edge in an annular groove formed in the attachment base, and with an actuating rod extending from the apex portion of the bimetal member thereby to actuate a fluid clutch at the distal end.
However, the conventional bimetal member 4 the type described above has the disadvantage that the temperatures at which deformation and restoration of the bimetal occur are widely different, therefore activation and deactivation of the fluid clutch occur at different temperatures.